AASHTO T 318-15 pdf free download

AASHTO T 318-15 pdf free download.Water Content of Freshly Mixed Concrete Using Microwave Oven Drying.
3. SUMMARY OF TEST METHOD
3.1. A test specimen of freshly mixed concrete is wrapped in a fiberglass cloth and dried in a microwave oven using a minimum of three drying intervals. The test specimen is broken up using a metal scraper, separating the coarse aggregate from the mortar throughout each of the drying intervals. A grinding pestle may also aid in separating the coarse aggregate from the mortar but is not required. The water content of the test specimen is calculated based on loss in mass of the test specimen at completion of the test. Total drying time is usually between 15 and 30 mm. Drying times are reduced if a higher wattage microwave oven is used.
4. SIGNCANCE AND USE
4.1. This test is for both laboratory and field measurements of water content in fresh concrete. The test results provide an estimate of the total water content in the fresh concrete and, with the absorption of the aggregates determined, provides an estimate of the mixing water content.
4.2. This test can be used as a quality control tool to check the water content of as-delivered concrete and to calculate the water/cement ratio if the cement content of the tested concrete is known.
4.3. Determine the water absorption of coarse and fine aggregates representative of the aggregates used in the concrete in accordance with T 84 or T 85, as applicable.
5. APPARATUS
5.1. Microwave Oven—A microwave oven with a minimum power setting of at least 900 watts, a turntable, and sufficient capacity to accept the specified tray and test specimen.
5.2. Glass Tray—A heat-resistant glass tray with dimensions of approximately 230 by 230 by 50 mm (9 by 9 by 2 in.).
5.3. Scale—A scale of sufficient capacity meeting the requirements of M 231, having a capacity larger than the sample plus tare, sensitive to 0. 1 g or less, and accurate to within 0.1 percent of the test load at any point within the range of use for this test method.
5.4. Metal Scraper—A small metal scraper having a sharp edge and a blade approximately 25 mm (1 in.) wide.
5.5. Grinding Pestle—A pestle having a porcelain grinding head with a diameter of approximately
50 mm (2 in.).
5.6. Scoop—Metal, hand held with a capacity of at least 1.2 L (40 oz).
6. MATERIALS
6.1. Fiberglass cloth—Plain weave fiberglass cloth having a mass of 0.34 kg/rn2 (10 oz/yd2) and a thickness of 0.35 mm (14 mil).
7. HAZARDS
7.1. Microwave radiation can be hazardous. Follow the safety precautions provided by the microwave oven manufacturer and OSHA at all times. Refer to the caution statements in T 255.
7.2. Aggregates with metallic inclusions can explode violently or melt and can be a fire hazard.
7.3. Materials and containers removed from the microwave oven may be hot, requiring the use of insulated gloves for safe handling.
8. SAMPLING TEST SPECIMENS
8.1. Obtain enough concrete to determine the density and the total water content of the concrete from the same sample of freshly mixed concrete as described in R 60.
8.2. Measure the density of the concrete in accordance with T 121M/T 121.
8.3. Test at least 1500 g of concrete obtained in one scoop after the sample is thoroughly mixed. Do not attempt to add mortar to achieve a specific specimen mass.
8.4. Protect the specimen from loss of moisture before the initial weighing.
8.5. Measure the initial mass of the test specimen within 5 mm after obtaining the composite sample of fresh concrete. Start the microwave drying procedure within 15 mm after obtaining the composite sample of fresh concrete.AASHTO T 318-15 pdf download.